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Lambert, Emma Constance

University of British Columbia

Fragility functions are integral to modelling building vulnerability in regional seismic risk models. Regional seismic risk assessments are often used to inform seismic policy development, even if there is often relatively low confidence in the suitability of the underlying fragility functions. This work investigates the defensibility of using generalized fragility functions when using regional seismic risk models to inform seismic policy development. This thesis presents a methodology to objectively quantify the impact that uncertainty in the fragility function damage state medians has on the variance the resulting regional seismic risk outputs, namely, casualties, building recovery time, and number of buildings with significant damage. This is achieved by means of a variance-based sensitivity analysis. The methodology is demonstrated by implementing this framework for the City of Vancouver, using a deterministic, active crustal, M7.2 earthquake scenario to represent ground shaking hazard and evaluating 15 fragility functions selected based on their contribution to the exposure and baseline risk. The findings indicate that variance in casualties is driven by uncertainty in the fragility function medians of pre-code era buildings, constructed prior to 1973, with light frame wood, unreinforced masonry, and concrete shear wall structural systems. This is attributed to their relatively low capacity and considerable presence within the broader exposure dataset. Similarly, the variance in building recovery time and significantly damaged buildings is driven by uncertainty in the medians of low-rise unreinforced masonry structures constructed prior to 1973 and light frame wood structures constructed from between 1973 and 2004. This sensitivity is driven by the underlying probabilities of damage that occur as a result of the shifts in the median damage states. Ultimately, this methodology provides a tool to better understand which input fragility functions can reduce uncertainty in regional seismic risk outputs, which is an important consideration when leveraging regional seismic risk models to inform policy decision making.

Text

2024-02-21

Attribution-NonCommercial-NoDerivatives 4.0 International

http://hdl.handle.net/2429/87464

Civil Engineering

University of British Columbia

UBCV

http://creativecommons.org/licenses/by-nc-nd/4.0/